FISHERY BULLETIN; VOL. 76, NO. 3 



provided by P. Kahsbauer (pers. commun., NMV, 

 1975). Steindachner's (1866) description is essen- 

 tially correct and unquestionably refers to D. 

 holocanthus. The placement of this specimen in 

 Atopumycterus was apparently based on the split 

 nasal tentacle (see section on D. nicthemerus). A 

 single split nasal tentacle was present on only 3 of 

 the more than 100 specimens of D. holocanthus 

 examined, so this condition is rare but not unpre- 

 cedented. 



Both D. liturosus Shaw and D. maculatiis 

 Lacepede (the Latinized version of Le Diodon 

 Tachete) have been incorrectly applied to D. 

 holocanthus by various authors (see section on D. 

 liturosus). 



For about the past 50 yr the chief sources of 

 confusion on the identity of D. holocanthus have 

 been confusion with D. histrix by some (mostly 

 American) authors and the lumping of D. liturosus 

 under D. holocanthus by nearly all authors. The 

 latter problem is discussed under D. liturosus. 



The confusion between D. hystnx and D. 

 holocanthus stems primarily from three sources. 

 Many authors (e.g., Gosline and Brock 1960) have 

 conjectured that D. holocanthus is the young of D. 

 hystrix because the former does not reach a large 

 size, and few, if any, small specimens of the latter 

 were available. However, as discussed under D. 

 hystrix, this species is pelagic to ca. 200 mm and is 

 thus unavailable to inshore collecting. Inasmuch 

 as D. holocanthus does not commonly exceed 200 

 mm, the confusion was perhaps understandable. 



Second, many early descriptions are poor and 

 keys often rely solely on the size of frontal spines 

 relative to the pectoral axil spines to distinguish 

 the two species. Especially in Atlantic specimens 

 of D. holocanthus, the frontal spines are likely to 

 be approximately the same size or even shorter 

 than the pectoral axil spines. 



Finally, as noted by Clark andGohar( 1953) (see 

 alsoBagniset al. 1972:225), living/), hystrix ohen 

 display a dorsal blotch pattern not unlike that of 

 D. holocanthus. I have not observed this color pat- 

 tern in preserved D. hystrix. 



The apparent divergence of the Atlantic and 

 Indo-Pacific populations of D. holocanthus men- 

 tioned above is of interest. At present, since D. 

 holocanthus is apparently absent from the Red Sea 

 and the Mediterranean, gene flow could occur only 

 around southern Africa. Evidence that this is ap- 

 parently not happening comes from the Indian 

 Ocean specimens which lack a snout spine and 

 have very long frontal spines in contrast to the 

 Atlantic specimens (Table 5). In addition, Poll's 

 ( 1959) description (as D. hystrix ) of a west African 

 specimen is typical of the specimens from the 

 western Atlantic examined by me. The apparent 

 increase in frontal spine length from the Atlantic 

 to the Pacific to the Indian Oceans is curious. 

 Based on studies of other groups (Ekman 1967) 

 affinities might be expected between the Atlantic 

 and eastern Pacific populations, but no extension 

 to Hawaii and Easter and Pitcairn Islands would 

 be expected. The lack of the snout spine in all but 

 the Atlantic population and one Hawaiian speci- 

 men may indicate that the Atlantic population is 

 distinct. Fin ray counts are of little help in resolv- 

 ing this question. Because all the characters 

 which appear to differ between the Atlantic 

 specimens and those from other areas are rather 

 variable (although some are significantly differ- 

 ent in a statistical sense), I choose not to distin- 

 guish formally the populations nomenclaturally 

 at the subspecific level. If future study shows this 

 split to be desirable, the proper name for the At- 

 lantic specimens would be Diodon holocanthus 

 pilosus Mitchill. 



Le Danois ( 1954 ) reported sexual dimorphism in 

 D. holocanthus, but her illustration of a female D. 

 holocanthus (p. 2355:fig. 3) appears to be D. 

 liturosus. 



Material examined. — 141 specimens, 5-289 mm. 



EASTERN PACIFIC: NMFS LJ (1;18.5) 18°56'N, 104 = 10 "W; 

 NMFS LJ D31-133.25 ( 1:64. 5l 26°04.5'N, 112°48.0'W; NMFS LJ 

 TO-5801 ( 1:85.5) 5°29.5'N, 77°57'W; NMFS LJ ( 1:73.5) "350 mi. 

 west of Costa Rica"; NMFS LJ B-5011 157.40 (2:41-41.5) 

 21°32.5'N, 111°14.5'W; UA 66-39-18 (1:242) San Agustin Bay, 

 Sonora, Mexico; UA 69-35-25 ( 1:245) Guaymas, Sonora, Mexico; 



Table 5. — Comparison of selected characters of Diodon holocanthus from five regions (see also 

 Figure 6). n = number of individuals examined for snout spine. 



564 



